Grid not responsive

Hi,
I'm trying to create a simple 3 grid layout. When I am viewing this in the editor it's working fine.

But when I view the updated version on the browser all hell breaks loose and I see huge images. I've tried everything.

Here's what I see in the editor: https://juhugym.com/wp-content/uploads/2021/03/Screenshot-2021-03-13-123146.jpg

Here's what it actually looks like in the browser: https://juhugym.com/

I followed this video from Mike https://youtu.be/VdfEj73i_kk but why does it not for me?
Regards